The micromagnetic Barkhausen signal is a parameter that is not measured in the production of amorphous magnetic films, ribbons, or fibers, and yet it can be useful in evaluating magnetic films, ribbons, or fibers since the signal depends on the differential permeability and is representative of the hysteresis curve of the material. The Barkhausen signal is described in detail by Jiles in the technical article entitled "Review of Magnetic Methods for Nondestructive Evaluation", NDT International, 21, 311, 1988, the teachings of which are incorporated herein by reference.
Micromagnetic Barkhausen measurements should be made when the average magnetization of the magnetic material changes from one direction to another. This indicates that the material should be close to its coercive point. Measurement of the micromagnetic Barkhausen signal thus requires a change in the magnetic field which can be accomplished by the spatial magnetic field gradient experienced by a given portion of the magnetic specimen as it moves through a coil. In the past, the Barkhausen signal has been measured with a stationary specimen which is subjected to a time varying magnetic field. However, when the specimen happens to be in motion, such as occurs during production of magnetic film, ribbon, or fiber, use of a time varying field to make such a Barkhausen signal measurement would involve complex synchronization of the position of a given portion of the specimen with the time varying field strength.
An object of the present invention is to provide a simple apparatus and method for measuring a Barkhausen or other signal of a moving film, ribbon, fiber or other magnetic material without the need for complex synchronization of the position of a given portion of the specimen with a time varying magnetic field.
Another object of the present invention is to provide apparatus and method for measuring a Barkhausen, or other signal, of a moving film, ribbon, fiber or other magnetic material, wherein components of the measuring apparatus are disposed stationary while the magnetic film, ribbon, or fiber is moving.